\input pstfig
$
\setcoorunit{4}{1}
\psset{xunit=0.4\psyunit}
%\drawaxes{-2.6}{5}{-3}{3.2}
\drawaxes{-3.5}{4}{-1.9}{1.9}
\markxlabel{0}{\scriptstyle O}{1em}
\uput[-20](0,1){\pi}
\uput[-180](0, 0.28){\nfrac{\pi}{2}}
\uput[-180](0,-0.73){-\nfrac{\pi}{2}}
%\psset{showpoints=true}
\psplot[algebraic=false]{ 0}{3}{x 1 atan 180 div}
\psplot[algebraic=false]{-3}{-0.0001}{x 1 atan 180 div 2 sub}
\thinline
\psplot[algebraic=false]{ 0}{3}{x 1 atan 180 div 1 add}
\psplot[algebraic=false]{-3}{-0.0001}{x 1 atan 180 div 2 sub 1 add}
\psplot[algebraic=false]{ 0}{3}{x 1 atan 180 div 1 sub}
\psplot[algebraic=false]{-3}{-0.0001}{x 1 atan 180 div 2 sub 1 sub}
\dashline
\psline(-3, 0.5)(3, 0.5)
\psline(-3,-0.5)(3,-0.5)
\psline(-3, 1.5)(3, 1.5)
\psline(-3,-1.5)(3,-1.5)
$
\bye
